Medical devices such as hemodialysis machines, medical infusion pumps, plasmapheresis devices, and the like often require the use of tubing to move fluids, e.g., to or from a subject for infusion. Such tubing can be made out of materials such as nylon, rubber, polyvinyl chloride, polyurethane, or polyethylene. However, control of the flow of fluids in the tubing is important in many applications.